PHILADELPHIA (AP) – A long-lost version of the Air Force One recordings made in the immediate aftermath of President John F. Kennedy’s assassination, with more than 30 minutes of additional material not in the official version in the government’s archives, has been found and is for sale.

There are incidents and code names described on the newly discovered two-plus hour recording, which predates the shorter and newer recording currently housed in the National Archives outside Washington and the Lyndon B. Johnson Library in Texas. The shorter recording was thought to be the only surviving version of the tape.

The asking price is $500,000 for the reel-to-reel tape, which is inside its original box with a typewritten label showing it was made by the White House Communications Agency for Army Gen. Chester “Ted” Clifton Jr.

It is titled “Radio Traffic involving AF-1 in flight from Dallas, Texas to Andrews AFB on November 22, 1963.”

“As Americans have looked to the history of the Kennedy assassination in search of answers, somewhere in an attic there existed a tape made years before the only known surviving version, of the conversations on Air Force One on that fateful day,” said Nathan Raab, vice president of The Raab Collection, a Philadelphia historic documents dealer that put the tape up for sale Tuesday.

The recording is the highlight of the personal effects from the estate of Clifton, who was Kennedy’s senior military aide and was in the Dallas motorcade when the president was assassinated.

Clifton, who died in 1991, had kept a collection of audio tapes, documents, photographs and video stemming from his years in the Kennedy and Johnson administrations. The Raab Collection, which is selling the tape and the rest of the archive, acquired the items at a public sale from Clifton’s heirs after the death of Clifton’s wife in 2009.

“At a time when there really wasn’t what we consider today a chief of staff, Clifton carried on many of those functions,” Raab said. “He retires in 1965, this goes with him.”

The recording consists of in-flight radio calls between the aircraft, the White House Situation Room, Andrews Air Force Base, and a plane that was carrying Kennedy press secretary Pierre Salinger and six Cabinet members from Hawaii to Tokyo when the president was assassinated.

The Clifton tapes include additional debate about whether Kennedy’s body would be brought to Bethesda Naval Hospital or Walter Reed Hospital for autopsy and if first lady Jackie Kennedy would accompany the fallen president, as well as expanded discussions about arranging for ambulances and limousines to meet the plane.

No references to Kennedy nemesis Air Force Gen. Curtis LeMay occur in the shorter version, but the Clifton tape contains an urgent attempt by an aide to contact him. The aide, seeking to interrupt Air Force transmissions to reach LeMay, is heard saying the general “is in a C140. Last three numbers are 497. His code name is Grandson. And I want to talk to him.”

The whereabouts of LeMay, whose enmity for the president makes him a central figure for Kennedy assassination researchers, have long been disputed. The newly discovered recording can finally end the speculation and pinpoint his location immediately after the president’s murder, Raab said.

Other conversations on the tape refer to “Monument” and “W.T.E.” — code names for people as yet unknown — and someone only called “John.”

Parts of the audio are difficult to discern because several conversations from the different patches are going on simultaneously. Raab said their digital recording was made as a straightforward recording, not as a forensic analysis, and current or future technology may be able to tease out and enhance the conversations.

The edited recording in the National Archives and the LBJ Library, available to the public since 1971, begins with an announcer stating it has been “edited and condensed” but not explaining how much was cut or by whom.

A more complete version of the Air Force One tapes were long sought but never found, adding fuel to decades-old suspicions that there is more to Kennedy’s assassination than the official account naming Lee Harvey Oswald as the lone gunman.

The Assassination Records Review Board, created by an act of Congress in 1992 after the Oliver Stone film “JFK” caused public uproar to re-examine Kennedy’s killing, unsuccessfully sought the unedited Air Force One tapes for its probe. Its final report in 1998, the board said the LBJ Library version was filled with crude breaks and chopped conversations.

“That this tape even exists will change the way we view this great event in history,” Raab said. “It took decades to analyze the shorter, newer version and it will take years to do the same here.”

The Clifton tape has been professionally digitized and a copy is being donated by the Raab Collection to the National Archives and the John F. Kennedy Library so the public will have access to the material even if the original tape is sold to a private collector.

The wholly unedited “raw” recording of the entirety of the trip, which also would have included periods of silence and static, has never been located. It would have been roughly 4 1/2 hours long.